It is known that caprolactone polyols are suitably employed in forming urethane coatings and that they offer a number of advantages over conventional polyester polyols. One of these advantages is that reaction of caprolactone polyols with polyisocyanates generally provides urethane coatings having better weathering characteristics. Clear coatings for exterior application are obtained from caprolactone polyols and aromatic polyisocyanates such as tolylene diisocyanates but such coatings tend to yellow due to the known light instability associated with aromatic diisocyanates.
It is also known that light stable urethane coatings are provided by reaction of caprolactone polyols with aliphatic diisocyanates.
It is disclosed in U.S. Pat. No. 3,896,303 to Gerkin and Comstock that adducts of polyepoxides and polycaprolactone polyols having functional hydroxyl groups, produced by reacting polycaprolactone polyols and polyepoxides, can be reacted with aliphatic polyisocyanates to produce polyurethane coatings useful in high performance applications. Such coatings exhibit the characteristics of high hardness, good impact resistance, low temperature flexibility, and chemical resistance. One of the disadvantages associated with the products obtained in this patent is their high viscosities, which present problems in their manufacture and use. This necessitates the addition of solvents, resulting in a lower total solids content. Consequently, cure requires more energy and the volatilization of the solvents causes atmospheric pollution.
It is an object of this invention to provide certain improved low viscosity polycaprolactone-based polyols which are especially useful in the formation of high performance coatings. These products have higher equivalent weight and substantially lower viscosity than the compositions disclosed in the prior art.
Another object is to provide polycaprolactone-based polyols which are used with particular advantage in forming light stable polyurethane coatings having a good balance of hardness, flexibility and abrasion resistance as well as weatherability, chemical resistance and high total solids content.
Various other objects and advantages of this invention will become apparent to those skilled in the art from the accompanying description and disclosure.